Question: Express your answer as a mixed number simplified to lowest terms. $18\dfrac{3}{20}-9\dfrac{3}{8} = {?}$
Answer: Find a common denominator for the fractions: $= {18\dfrac{6}{40}}-{9\dfrac{15}{40}}$ Convert ${18\dfrac{6}{40}}$ to ${17 + \dfrac{40}{40} + \dfrac{6}{40}}$ So the problem becomes: ${17\dfrac{46}{40}}-{9\dfrac{15}{40}}$ Separate the whole numbers from the fractional parts: $= {17} + {\dfrac{46}{40}} - {9} - {\dfrac{15}{40}}$ Bring the whole numbers together and the fractions together: $= {17} - {9} + {\dfrac{46}{40}} - {\dfrac{15}{40}}$ Subtract the whole numbers: $=8 + {\dfrac{46}{40}} - {\dfrac{15}{40}}$ Subtract the fractions: $= 8+\dfrac{31}{40}$ Combine the whole and fractional parts into a mixed number: $= 8\dfrac{31}{40}$